The identity and topographic localization of infiltrating cells such as inflammatory and tumor cells and their products in patient specimens are analyzed by immunohistochemistry, in situ hybridization, polymerase chain reaction (PCR), microdissection and image analysis. Using these techniques we will make an accurate pathological assessment of disease from the studied tissue, guide an appropriate treatment for the patient, and understand the pathogenesis of the disease. In FY2001 we have continued and accomplished the following research: 1. Detection of Genes and Proteins in Primary Intraocular Lymphoma Cells. Using microdissection and PCR techniques we detected the presence of DNA from several infectious agents including Toxoplasma gondii in primary intraocular lymphoma, but not normal cells in the eye. We speculated that Toxoplasma gondii might play a role in some forms of primary intraocular lymphoma. Additionally, we further reported the association between B-cell lymphoma, high intravitreal IL-10 level and IL-10:IL-6 ratio greater than 1. We suggest that this could be used to improve the diagnostic yield for this tumor. 2. New Pathology and Pathogenesis of Ocular Inflammation and Other Diseases. We detected T-cell receptor gene rearrangement and HTLV-1 gag gene in conjunctival T-cell lymphoma caused by HTLV-1 infection. We reported no retinal toxicity in relatively high dose of intravitreal ganciclovir and foscarnet treatment for cytomegalovirus retinitis in AIDS patients. In addition to cataracts, peripheral retinal changes including retinal tuft and degeneration are found in Hajdu-Cheney syndrome. Apoptosis of the corneal cells plays a role in pathogenesis of Fuchs endothelial dystrophy. 3. Experimental Models for Various Non-Inflammatory Ocular Diseases. In collaboration with several laboratories in the NIH, we reported that thymosin beta 4 promotes corneal wound healing and suppresses inflammatory response induced by trauma. Structural abnormalities including the brain and retina, retinal dysplasia, develop following ablation of the gene encoding nonmuscle myosin II-B heavy chain. Congenital nuclear cataracts and mild uveitis are observed in HIV-transgenic mice. These findings demonstrate that ocular pathology is an important manifestation of various systemic diseases.